1. Technical Field
The present invention relates to a projection type display system having a position detection function capable of projecting an image and optically detecting a position of a target object located within a detection area determined on the projection side of the image.
2. Related Art
Recently, an electronic device such as a cellular phone, a car navigation system, a personal computer, a ticket machine, and a bank terminal unit includes a display system having a position detection function as a unit which has a touch panel on a front surface of an image producing device such as a liquid crystal device. According to this display system having the position detection function, information is inputted while referring to an image displayed on the image producing device. The touch panel is constituted by a position detection device for detecting a position of a target object within a detection area (for example, see JP-A-2001-142643, FIG. 6).
The position detection device disclosed in JP-A-2001-142643 is an optical type device which has a detection area on the image display surface side of a direct viewing type display system and includes a plurality of light emitting diodes and a plurality of photo-transistors on one side and the other side of the detection area, respectively. According to this position detection device, a position of a target object entering the detection area and blocking light can be detected by specifying the photo-transistor to which supply of the light is blocked by the target object.
The present inventor intends to propose a novel display system, i.e., a projection type display system having a position detection function which determines a detection area on the image projection side such as in the vicinity of a screen and detects a position of a target object located within the detection area. When the structure disclosed in JP-A-2001-142643 is applied to the novel projection type display system having the position detection function, a number of light emitting diodes and photo-transistors are required to be disposed around the detection area. This type of projection type display system having the position detection function is difficult to be put to practical use.